The Rise of Islam simulates the rapid expansion of Islam in the 7th Century. It starts in 627 when the nation owning Mecca converts to Rashidun, a Sunni nation with permanent claims on the Middle East and North Africa. They also get a powerful modifier, "The Rise of Islam", for 50 years which makes their armies extremely difficult to defeat and the ability to auto-annex and auto-convert land that they occupy.

Upon enacting "Form the Mongol Empire", you'll be temporarily given huge bonuses to your military and a mechanic that allows you to auto-annex occupied provinces after holding them for at least six months. Upon annexing the province you will receive the province and a free core. Use this as much as you can since this only lasts 60 years.

When you begin the game before the base game's starting point you cannot select the original ideas. This prevents player from starting a mass colonial empire in the Roman era. Instead you must select from a variety of "early ideas". The base game ideas aren't even visible until you reach administrative tech level 49. Upon reaching level 49 you will unlock another idea slot and access to both the early ideas and the normal ideas.